Input devices including proximity sensor devices (also commonly called touchpads or touch sensor devices) are widely used in a variety of electronic systems. A proximity sensor device typically includes a sensing region, often demarked by a surface, in which the proximity sensor device determines the presence, location and/or motion of one or more input objects. Proximity sensor devices may be used to provide interfaces for the electronic system. For example, proximity sensor devices are often used as input devices for larger computing systems (such as opaque touchpads integrated in, or peripheral to, notebook or desktop computers). Proximity sensor devices are also often used in smaller computer systems (such as touch screens integrated in cellular phones).
Many commercially available proximity sensor devices utilized capacitive and optical sensing. Capacitive sensing, although having a robust history of use, is susceptible to geometric distortion or edge effects at the perimeter of the sensing region, and is also susceptible to damage and/or inaccurate output due to electromagnetic interference (EMI) and electromagnetic discharge (ESD). Moreover, capacitive sensing is limited to the detection of conductive objects relative to the sensor, thus limiting the types of inputs devices which may be utilized. The accuracy of optical sensing devices may be diminished due to the effects of dirt, oils and other contaminants.
Ultrasound sensing has been recognized as a potential improvement for next generation touch panel devices. However, significant challenges remain in the development of ultrasound sensing prior to acceptance for commercially viable use.
Therefore, there is a need for an improved subsystem, system and method for sensing an input object relative to a sensing region of an ultrasound sensor device.